The invention relates generally to thermal transfer devices, and particularly, to alignment and spacing of electrodes in thermal transfer devices.
Thermal transfer devices may be used for a variety of heating and cooling systems, such as refrigeration, air conditioning, electronics cooling, industrial temperature control, power generation, and so forth. These thermal transfer devices are also scalable to meet the thermal management needs of a particular system and environment. Unfortunately, existing thermal transfer devices, such as those having refrigeration cycles, are relatively inefficient due to mechanical components such as compressors.
In contrast, solid-state thermal transfer devices offer certain advantages, such as the potential for higher efficiencies, reduced size, and so forth. For example, thermotunneling devices transfer heat by tunneling electrons from one electrode to another electrode across a nanometer-scale gap. The heat transfer efficiency of these thermotunneling devices depends upon various factors, such as, material characteristics, electrode alignment, electrode spacing, and so forth. For efficient operation of these thermotunneling devices, the electrodes may be mirror images of one another and spacing between the electrodes may be on the order of 1-10 nanometers. Unfortunately, electrode spacing is particularly difficult to achieve and maintain in these thermotunneling devices. Thus, achieving efficient thermotunneling devices can be problematic.
Certain thermotunneling devices have electrodes that are disposed about a sacrificial layer, which is removed during fabrication to create a gap between the electrodes. This fabrication method involves forming a composite by placing a sacrificial layer between two electrodes. Subsequently, the fabrication method splits the composite into two matching electrodes by removing the sacrificial layer, while preserving the physical position of the electrodes. In some cases, external piezo positioners are used to align the electrodes and maintain a gap between the two electrodes. In such systems, the spacing of nanometer precision is difficult to achieve and the two electrodes are not aligned to the desired precision or consistency. Further, incomplete removal of the sacrificial layer may be deleterious to the quality of surface matching of the two electrodes, and may also disrupt the tunneling of electrons.
Accordingly, a need exists for relatively precise control of the spacing and alignment between adjacent electrodes of a thermotunneling device.